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A new international research rewrites the history of reptiles starting from a fossil found in the Dolomites.

The origin of lizards and snakes should be pushed back by about 75 million years, as documented by a small reptile, Megachirella wachtleri, found almost 20 years ago in the Dolomites and rediscovered today thanks to cutting-edge techniques in the field of 3D analysis and the reconstruction of evolutionary relationships. Evidence to this effect has been provided by an international paleontological research with the participation of the MUSE Science Museum of Trento, in collaboration with the “Abdus Salam” International Centre of Theoretical Physics of Trieste, the Enrico Fermi Centre of Rome and Elettra Sincrotrone Trieste. The results have been published in the prestigious science journal Nature, which has also dedicated its cover image to research.

The international team has identified Megachirella wachtleri – a small reptile which lived approximately 240 million years ago in what are today the Dolomites – the most ancient lizard in the world thereby providing key insight into the evolution of modern lizards and snakes.
The data – obtained by 3D X-ray imaging techniques and the analysis of DNA sequences – suggest that the origin of “squamates”, i.e. the group comprising lizards and snakes,is older than previously thought and that it can be dated to approximately 250 million years ago, before the most extensive mass extinction in history.

“The specimen is 75 million years older than what we thought were the oldest fossil lizards in the world”, explained Tiago Simões, from the University of Alberta, Canada, lead author of this research, “and provides valuable information for understanding the evolution of both living and extinct squamates”.

“The amount of processed data is such as to leave no doubt on the reliability of the obtained result – stressed Massimo Bernardi, paleontologist of MUSE of Trento. “This small reptile, which can surely be regarded as one of the most important fossil remains ever found in our country, will be a reference for paleontologists and anyone who is to study or describe the evolution of reptiles from now on. Megachirellais a sort of Rosetta stone, a key to the understanding of an evolutionary event that has affected the history of life on this planet forever”.

Today our planet is inhabited by approximately 10,000 species of lizards and snakes, almost twice as many as the mammal species. Despite this diversity, until now the origin and the first stages of reptile evolution had remained wrapped in mystery.
Discovered in the first years of 2000 in the Dolomites of Trentino–Alto Adige, Megachirella wasfirstinterpreted as an enigmatic reptile similar to a lizard. However, the impossibility to extract the specimen from the rock containing it and the lack of comparable material did not allow a precise reconstruction of its evolutionary relationship with other reptiles.

For a better understanding of its anatomy, Megachirella has been analysed by X-ray computed microtomography (microCT) at the Multidisciplinary Lab of the “Abdus Salam” International Centre for Theoretical Physics (ICTP) in collaboration with “Elettra Sincrotrone Trieste”. The microCT technique is similar to the hospital CT systems, but at much greater detail. It can produce a virtual 3D model of the external and internal parts of the analysed specimens with micrometer resolution. It also allows to virtually separate different sample components, such as a fossil from its rocky matrix.“When the MUSE colleagues took the Megachirellafossil to Elettra, I was enthusiastic at this opportunity and at the same time aware of the technical difficulties that a microCT analysis could entail” – explains Lucia Mancini, researcher at the Elettra international research facility. “Thanks to the collaboration with ICTP and by using suitable tools to analyse the 3D images, we have succeeded in virtually separating the skeleton from the rock”. “As soon as we saw the results of the analysis, we realised that, after millions of years, we were the first to observe the underside of Megachirella, i.e. the side embedded in the rock: it was a great thrill” adds Federico Bernardini, researcher at ICTP and Fermi Centre.

The data obtained thanks to virtual imaging have been added to the largest dataset ever assembled comprising lizards, snakes and their close relatives, and have been analysed by means of state-of-the-art methods capable of reconstructing relationships between species. Thus, this small, previously enigmatic, reptile has been fitted into the tree of life, it being the most ancient known squamate.

Thanks to the spectacular reconstruction of a living Megachirella– by the multiple-award-winning Milajn paleoartist Davide Bonadonna –the research has also made it to the journal cover, which had not dedicated its prestigious opening image to an Italian fossil for twenty years.

IN-DEPTH STUDY BY MUSE – SCIENCE MUSEUMwww.muse.it
For over three decades the Geology and Paleontology section of MUSE has been studying the geo-paleontological diversity in the Dolomites area. The recent research projects on the effects of the great environmental changes occurred in the history of planet Earth have led to a new analysis of rock successions and fossil findings that have been integrated into global-scale analysis, thus demonstrating the importance of the geo-paleontological heritage of the Dolomites and offering new interpretations of our remotest past.

The study published in Nature today is the result of years of observations and analyses, initiated thanks to the collaboration with Evelyn Kustatscher from the Natural Science Museum of Alto Adige and Silvio Renesto from Insubria University, which developed into a complex protocol of analysis and the development of a new interpretation model of the great global crisis, in particular of the most extensive mass extinction in history, occurred 252 million years ago. An event which brought about the end of many groups of organisms but which, as this study also demonstrates, became an opportunity for others.

The study is part of the project “The end-Permian mass extinction in the Southern and Eastern Alps: extinction rates vs. taphonomic biases in different depositional environments” funded by the Euregio Science Fund.

IN-DEPTH STUDY BY THE “ABDUS SALAM” INTERNATIONAL CENTRE OF THEORETICAL PHYSICS (ICTP) OF TRIESTE AND ELETTRA SINCROTRONE TRIESTEwww.ictp.it, www.elettra.trieste.it
The researchers of Elettra Sincrotrone Trieste and the “Abdus Salam” International Centre of Theoretical Physics (ICTP) of Trieste have contributed to this study with an accurate and non-invasive analysis of the lizard fossil, with the aim of safeguarding its integrity and, at the same time, revealing its hidden features. Cutting-edge technologies were used, in particular those available at the Multidisciplinary Lab (MLab) of ICTP specifically dedicated to the cultural and archeological, and the fruit of the collaboration between the two centres. The laboratory, co-funded by the Fermi Centre of Rome, is equipped with a range of portable equipment for X-ray radiography, microtomography, fluorescence and diffraction used for both research activity and the training of students and scientists from developing countries.

The Multidisciplinary Lab of ICTP
The ICTP Multidisciplinary Lab (MLab) hosts activities promoting interdisciplinary experiments and applied physics. The world-class scientific activities carried out by the Lab include the planning of integrated digital circuits and the development of innovative technologies allowing to observe matter by x-ray analysis, from rocks to the historical and archeological heritage, without damaging them.
The Laboratory collaborates with several scientific research institutes, both local and international, in order to offer hands-on training to scientists from developing countries, so that theoretical studies can be transformed into practical applications.